Megaman bulbs are usually excellent in my experience but these were not up to the job.
I replaced two 40 watt incadescent bulbs controled by a dimmer switch with these (my dimmer is suitable for low loads in case anyone is wondering if it was the dimmer rather than the bulbs). The bulbs would initially come on OK but after a while I would notice them flickering very quickly. By turning down the dimmer switch I could get them on constant again but after a couple of weeks of this I'd had enough.
When I removed the bulbs I found one of them had develped a crack on the inside ! The bulb is covered in some kind of soft plastic wrapper so you can clearly see the damage is from inside the bulb. This is worrying and I'm glad I removed them when I did.
Given this experience I went down to Homebase and bought a batch lot of old style 40 watt bulbs to last me the next few years whilst they hopefully develop energy saving bulbs that can cope with dimmer switches.